A number of ball joints have been conventionally known. For instance, Japanese utility model publication (kokoku) No. 63-39452 discloses a ball joint equipped with a dust cover. According to this prior art, as illustrated in FIG. 7, the ball joint comprises a housing 51 defining an inner chamber and having an open end, a ball seat member 53 fitted into the inner chamber of the housing 51, a ball stud 52 having a spherical head disposed in a cavity defined in the ball seat member 53 and a stem portion connected to this spherical head and extending out of the open end of the housing 51, and a dust cover 54 extending between the housing 51 and the external surface of the stem portion of the ball stud 52. An annular recess 55 is formed around the outer circumferential surface of the open end of the ball seat member 53, and an annular bead 56 provided on the peripheral edge of the associated end of the dust cover 54 is fitted into this annular recess 55. Furthermore, a thin walled open end portion 57 of the housing 51 is crimped onto the entire outer circumferential surface of the open end of the ball seat member 53 with the result that the ball seat member 53 is firmly secured in the housing 51 and the bead 56 of the dust cover 54 is firmly retained in the annular recess 55.
According to this structure, one can obtain the advantage that the dust cover 54 can be secured without using any clips for securing purpose. However, because uniformly deforming the open end portion 57 of the housing 51 is highly difficult to accomplish, and excessive local deformations tend to occur, a high dimensional precision must be maintained. Furthermore, it is difficult to stabilize the securing force and the sealing capability. Various measures can be taken, but such measures will increase the fabrication cost. Thus, crimping for securing a dust cover has various shortcomings.